C-reactive protein to albumin ratio as a prognostic marker in community-acquired pneumonia mortality

Aim: This study aimed to evaluate the prognostic value of the C-reactive protein-to-albumin ratio (CAR) in predicting 30-day mortality among patients diagnosed with community-acquired pneumonia (CAP) presenting to the emergency department (ED). Material and Methods: A retrospective study was conducted on 312 patients diagnosed with CAP who presented to the ED of a tertiary care hospital between January 1, 2022, and January 1, 2024. Demographic, clinical, and laboratory data were collected, including C-reactive protein (CRP) and albumin levels. CAR was calculated by dividing CRP levels (mg/dL) by albumin levels (g/L). The primary outcome was 30-day mortality. The prognostic performance of CAR was evaluated using receiver operating characteristic (ROC) curve analysis. Results: Of the 312 patients included, 87 (27.9%) died within 30 days. The deceased group had significantly higher CAR values compared to survivors (1.18 ± 0.62 vs. 0.52 ± 0.25, p < 0.001). CAR demonstrated excellent discriminatory power for predicting 30-day mortality, with an area under the curve (AUC) of 0.837 (95% CI: 0.791–0.876, p < 0.001). At a cut-off value of >0.77, CAR achieved a sensitivity of 75.9% and a specificity of 86.7%. Deceased patients also exhibited significantly lower systolic and diastolic blood pressures, oxygen saturation, and albumin levels, along with higher CRP levels and respiratory rates. Comorbidities such as stroke and congestive heart failure were more prevalent in the deceased group compared to survivors. Conclusion: The C-reactive protein-to-albumin ratio is a reliable prognostic marker for predicting 30-day mortality in CAP patients presenting to the ED. Its ease of calculation and strong discriminatory power make CAR a valuable tool for risk stratification and clinical decision-making. Prospective studies are warranted to confirm these findings in diverse populations.